In the clinical laboratory field, techniques for separating serum or plasma from blood by centrifugation using a difference in the specific gravities between blood components are widely used. In order to prevent the separated components from mixing again, various serum- or plasma-separating compositions having a specific gravity adjusted to 1.03 to 1.08 have been conventionally suggested.
As the above-described serum- or plasma-separating composition, thixotropic compositions have been widely used, from the viewpoint of stability during transport and storage, and also from the viewpoint of enabling stable maintenance of a separated state even after centrifugation. Use of a thixotropic composition can simplify blood separation, irrespective of skills of the user.
The following Patent Literature 1 discloses a serum- or plasma-separating composition comprising a liquid organic compound component, and an inorganic powder dispersed in the liquid organic compound for the purpose of adjusting the specific gravity and imparting a thixotropic-property. Patent Literatures 1 and 2 disclose serum- or plasma-separating compositions comprising various organic compounds such as a polyoxyethylene polyoxypropylene block copolymer or a silicone-based surfactant as a thixotropic-property enhancer.